Antiwear performance and mechanism of an oil-miscible ionic liquid as a lubricant additive

Jun Qu, Dinesh G. Bansal, Bo Yu, Jane Y. Howe, Huimin Luo, Sheng Dai, Huaqing Li, Peter J. Blau, Bruce G. Bunting, Gregory Mordukhovich, Donald J. Smolenski

Research output: Contribution to journalArticlepeer-review

316 Scopus citations

Abstract

An ionic liquid (IL) trihexyltetradecylphosphonium bis(2-ethylhexyl) phosphate has been investigated as a potential antiwear lubricant additive. Unlike most other ILs that have very low solubility in nonpolar fluids, this IL is fully miscible with various hydrocarbon oils. In addition, it is thermally stable up to 347 °C, showed no corrosive attack to cast iron in an ambient environment, and has excellent wettability on solid surfaces (e.g., contact angle on cast iron <8°). Most importantly, this phosphonium-based IL has demonstrated effective antiscuffing and antiwear characteristics when blended with lubricating oils. For example, a 5 wt % addition into a synthetic base oil eliminated the scuffing failure experienced in neat oil and, as a result, reduced the friction coefficient by 60% and the wear rate by 3 orders of magnitude. A synergistic effect on wear protection was observed with the current antiwear additive when added into a fully formulated engine oil. Nanostructure examination and composition analysis revealed a tribo-boundary film and subsurface plastic deformation zone for the metallic surface lubricated by the IL-containing lubricants. This protective boundary film is believed to be responsible for the IL's antiscuffing and antiwear functionality.

Original languageEnglish
Pages (from-to)997-1002
Number of pages6
JournalACS Applied Materials and Interfaces
Volume4
Issue number2
DOIs
StatePublished - Feb 22 2012

Keywords

  • additives
  • antiwear
  • boundary film
  • lubricants
  • oil-solubility
  • phosphonium-based ionic liquids

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